Highly original and influential (7)
I believe the answer is:
seminal
'highly original and influential' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for seminal that I've seen before include "Menials giving rise to new beginnings" , "Of beginnings or early developments" , "Having strong later influence" , "Major" , "Highly original" .)